Ethanol and ozone sensing characteristics of WO3 based sensors activated by Au and Pd

The sensitivity towards ethanol (C2H6O) and ozone (O3) of WO3 thin films based conductometric sensors was investigated. The performances of three sensing layers were compared: bare WO3, palladium (Pd) and gold (Au) activated surface WO3. The WO3 thin films were deposited by thermal evaporation of oxide powders onto SiO2/Si transducers with platinum interdigited electrodes. All the tests were performed at the same working temperature Twork = 300 °C and under fixed gas concentrations: 2% ethanol and 0.8 ppm ozone using dry air as carrier gas. The morphology of the sensor surfaces were analyzed before and after working runs by atomic force microscopy (AFM) and scanning electron microscopy (SEM) in order to control the stability of the metal deposits. DC and AC electrical responses under 50 l h−1 gas flows are presented and discussed.